Support for electro-acoustic transducer



June 16, 1964 c. P. GLOVER SUPPORT FOR ELECTRO-ACOUSTIC TRANSDUCER Filed Au 25, 1955 1 PRIOR ART lllIl' IN VEN TOR. 61. V05 P. 64. a VER fju%. Z

United States Patent 3,137,836 SUPPORT FOR ELECTED-ACOUSTIC TRANSDUCER Clyde P. Glover, West Brookfieid, Mass., assignor to the United States of America as represented by the Secret of the Navy my Filed Aug. 25, 1955, Ser. No. 530,651

3 Claims. (Cl. 349-) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to supports for transducers and more particularly to supports for electro-acoustic transducers intended for underwater operation.

The conventional means for supporting the vibrating element, viz; the ferroelectric, electrostrictive, or piezoelectric vibrator which may be a polarized barium titanate crystal, or the like, with the usual electroded faces, has been to rest one face of the vibrator on a fiat surface and to compress a gasket against the other face to provide a pressure seal. The use of such a seal has many disadvantages. For example, although the vibrating element should be supported at its node to prevent undesirable damping, with this type device the vibrator cannot be so clamped. Another disadvantage is the possibility of damage to the vibrating element because of overcompression of the gasket. Still another disadvantage is the necessity of using insulating washers or spacers to achieve electrical isolation of the vibrator.

It is, accordingly, a primary object of the present invention to provide a support for the vibrating element of an electro-acoustic transducer wherein said element is clamped at a node and the effects of non-uniform clamping pressure are substantially reduced.

It is a further object to provide a support for the vibrating element of an electro-acoustic transducer wherein the need for insulating Washers or spacers is eliminated and wherein the assembly of the transducer is facilitated by the capability of preassembling the vibrating element and the associated gasket into one unit.

It is another object to provide a support for the vibrating element of an electro-acoustic transducer wherein said vibrating element is easily replaceable because the support permits electrical contact without the use of soldered connections.

Another object is to provide a support for a vibratile disc which will have a minimum of adverse effect on the vibrations of the disc.

One feature of the present invention resides in the support of the vibrating element mainly at its peripheral edge surface.

Another feature resides in the provision by the support of a pressure seal.

Still another feature resides in the provision of a pressure seal which also electrically insulates the vibrating element from the other components of the transducer assembly.

In accordance with the present invention, there is provided an electro-acoustic transducer which comprises an electromechanical vibrator having substantially parallel (electroded) major surfaces and a perimeter edge surface which is substantially perpendicular to the major surfaces. Resilient means are provided for intimately embracing and supporting the vibrator at its perimeter and a housing is provided for receiving the resilient means and embraced vibrator. The housing includes means for compressing the resilient means in a manner to cause the latter to firmly grip the vibrator at its perimeter.

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There is also included means for making electrical contact with the vibrator.

Also, there is provided in accordance with the present invention an electro-acoustic transducer which comprises a substantiallycircular electro-mechanical vibrator, which may be made of barium titanate, and which has substantially parallel major surfaces and a perimeter edge surface which is substantially perpendicular to said major surfaces. A ring of an elastomeric material having an inner circumference substantially equal to the circumference of the vibrator snugly embraces the latter on its edge surface. There is provided a housing for receiving the ring and vibrator, the housing including a first tubular member wherein the inner circumference of a first portion is substantially equal to the outer circumference of the ring and a second portion wherein the inner circumference is smaller than the first portion whereby a first circular shelf is provided for resting the elastomeric ring, and a second tubular member for threadably receiving the first member and for compressing the ring. Means for making electrical contact with the vibrator is provided which includes a Phosphor bronze spring.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

FIG. 1 is a cross sectional depiction of the heretofore used arrangement for supporting the vibrating element of an electro-acoustic transducer; and

FIG. 2 is a cross sectional depiction of an embodiment of the present invention.

Referring now to FIG. 1, there is shown a support or member 10 which may be tubular having a threaded section on its outer periphery 12 and portions 14, 16 and 18 of increasingly smaller inner diameters. With the arrange ment of three portions having different diameters, circumferential inner shelves 20 and 22 are provided. A piezoelectric vibrating element 24 has one of its surfaces 25 resting on washer 26 which in turn rests on shelf 22. The vibrating element 24 may be formed of a suitable piezoelectric material or a ferroelectric material such as barium titanate or the like. As shown, element 24 does not make contact with the inner peripheral surface of member 10 and face 25 is prevented by means of washer 26 from contacting shelf 22. Resting upon face 27 of element 24 is a gasket 28. Member 10 threadedly engages a member 11 at its threaded portion 12 and as a consequence of such engagement, compresses gasket 28. Members 10 and 11 may consist of a suitable resistive material such as a steel alloy and the like. Resting upon shelf 20 is an element 30 which has aflixed thereto an electrically conductive spring contact 32 and its associated lead for making electrical contact with face 25 of element 24. In the arrangement of FIG. 1, uniform clamping pressures are not applied to element 24 andthe element cannot be clamped at a node. Overcompression of gasket 28 can lead to damage of element 24. Spacer or washer 26 is required to achieve electrical isolation of element 24. It will be observed that with this construction, the vibrating element 24 could not be clamped at a node thereof. In order to prevent undesirable damping of a vibrating element, the element must be supported at its node, that is, at point which there is minimum or zero vibration.

Referring now to FIG. 2, there is shown a similar arrangement as that shown in FIG. 1, however in this figure, the vibrating or vibratile element or disc 34 which has parallel, approximately fiat faces is peripherally encircled by an elastomeric gasket 36 such as an O-ring gasket, the element 34 fitting snugly into the inner opening thereof. The outer circumference of ring gasket 36 is closely re- 3 ceivedwithin the portion 14 having the largest inner dimeter n. m mbe 9 w he i a t 35 restin on shelf 22'. It is seen that when member 10' threadably engages member 11, as the engagement is tightened, pressure is brought to bear on ring gasket 36 causing it to be compressed against shelf 14' and since the outer periphery of the ring is confined against substantialradial expansion, the ring, will be' distorted radially inwardly of itself and into firm pressure contact against the peripheral edge surface of the vibrator, thusv consequently causing it to grip element 34 along its perimeter. This forms a pressuretight seal between the periphery of the element 34 and the gasket. The element 34 is a thin right. circular cylinder which is excited so that its faces vibrate in directions. parallel to the axis of the cylinder, during which the thickness of the cylinder, which is the distance between the faces,

varies with the vibrations. When such a body expands in' thickness, such as the lengthalong the axis of the cylinder, the body, when free to do so, expands equally in both axial directions from a'central plane which is parallel to the faces. Hence, there is no movement of the cylinder at this central plane during the vibration, so that this plane of substantially no motio'n'during the vibration can "be called a nodal plane. The ring 36 which engages the peripheral side edge of the cylinder best engages with the cylinder edge surface at this middle plane, called the nodal plane, that supports the cylinder whereit has its minimum or no motion, and hence, it exerts a minimum damping of the vibration of the thin cylinder. Since it is physically impractical to support a cylinder along a line only, the'contact of the support with the cylinder should be centered along this middle or nodal plane of the vibrating element or cylinder. It is necessary for the perimetric edge surface of element 34 to be substantially perpendicular. to its back surface35 and its radiating surface 33. As is shown in FIG. 2, electrical contact is made to the back surface 35 with a Phosphor bronze spring or pressure contact 32.. Of course, if it is desired, electrical coiltact may, be made to the radiating'surface 33. of element 34 with the pressure contact 32'. i a

' With the arrangement of FIG. 2, as ring gasket 36 is compressed it is forced radially inwardly and caused to grip element 34 around its peripheral edge surface of the element, and also into a pressure-tight seal withthe inner circumference on memberltl'. Ring gasket 36 also provides electrical isolation of element 34 so that it is not necessary to make use of a spacer or washer 26 as shown FIG. 1 Also, since electrical contact is made to ele ment 34. with pressure contact 32", the element 34 may be readily replaced by another vibrating. element without having to unsolder any electrical connections.

FIG. 2 it will be noted that the support 10' has a recess, including the portion 14, that opens outwardly through an end face of the support, and this recess has a rabbet or annular groove around its periphery with the. shelf 22 forming one Wall of this groove andthe adjacent outer'end part 14' of the peripheral wall of such recess forming another wall of this groove that is approximately perpendicular to the shelfwall 22'. The elastomeric ring or element 36 h'asporti'ons on opposite sides of the recess in the groove, that fit against both walls of the groove. The vibratile disc or. element 34 has parallel plane faces and a peripheral edge wall'or face that is perpendicular to the planes of the large or main faces of this disc. This peripheral edge wall,v of element 34 is snugly received and.

confined between the elastomeric element portions or means 3 6 at. opposite sides of the recess, so that the vibratile element or disc will be mainly supported frictionally by the pressure of this elastomeric member solely on the peripheral edge wall of disc 34. 'In the embodiment of the invention illustrated in FIG. 2, this recess in the support is cylindrical in shape,' and the elastomeric member is'an endless ring, generally circular in transverse cross-section. The disc 34 has its peripheral edge snugly engaged with and supported by the inner periphery of this elastomeric ring. Because of the circular, transverse cross-section of this ring, the portions of the ring surface adjacent its inner periphery recede away from the opposite faces of the disc 34, and are entirely out of contact 7 with the faces of the disc 34. The cap or member 11 is threaded on the body or support 10' at the end of the support having the recess in which the vibratile element or disc is mounted, for movement toward and from the hot- I tom of rabbet groove, and has a portion that engages the,

V the main support through frictional engagement with the edge wall of the disc, for the disc,'while leaving the "disc free to vibrate in any pattern'within its entire face areas. While this disc 34 may bean electrostrictive or' piezoelectric element, 'or a barium titanate disc, the invention as disclosed relates broadly to the support of any vibratile element or disc, usually planar, by elastomeric meansthat engages the vibratile element or disc solely on its periphl eral edge wall, and is out of contact with the faces of such 7 element or disc so as to leave the faces of such vibratile element or disc uncovered and free to vibrate in any" pattern. This frictional pressure on the disc edge is variable by varying the pressure on the elastor'neric'means' Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It'is therefore to be understood that within the scope of the appended claims the invention may'be practiced otherwise than as specifically described;

' I claim:

1. A vibratile disc and its support, which comprises a member having a recess opening'through a facethereof, said member having an endless rabbetvvith two walls at angles to one another bordering said recess and opening outwardly of the recess and at its inner side into said recess, an endless elastomeric element disposed in said rabbet and abutting said two'walls of said rabbet, a vibrja-' tile disc having a marginal edge face substantially perpendicular to its other faces, disposed across said recess with its said marginal edge face abutting the inner periph cry of said element, and means carried by said member and adjustable thereon in a direction normal to the planes of said other faces of 'said disc to confine said element in said rabbet and compress it against said two wallsjand, said marginal edge face under a pressure varyingwith the said adjustment of said means, the inner periphery. of said elastomeric element, in transverse cross-section receding outwardly from and out of contact with the faces of said disc, abutting said disc solely along itssaid marginal edge, and forming the main support for said disc;

' 2. A vibratile element and its support, which comprises a support member having therein a chamber" that opens outwardly through a face of said member, said, member having an endless rabbet around said chamber opening towards said face, and also at about right angles thereto into the chamber, an endless elastomeric rin'gmernber, disposed in said rabbet, abutting its walls, and project,- ing outwardly of said groove towards said end'face'for a distance slightly beyond said rabbct, a plate-likevibratile element disposed across said chamber and having its marginal edge wall approximately 'perpendicular'to its faces and abutting frictionally with, and 'mainly'sup ported by, the inner periphery' of said elastomeric member, and means adjustable on said support memberffor movement toward and from said rabbet and engaging.

said elastomeriemember, confining it in said rabbet and, deforming it in said rabbet in a direction inwardlyof the chamb'er'into firmer contact with said marginal edge Wall l of said vibratile element and increase the pressure of said elastomeric member on the marginal edge face of vibratile element, said elastomeric member being always free of any substantial contact with the faces of said vibratile element.

3. The construction according to claim 2, wherein said elastomeric member along its inner periphery is convex in transverse cross-section.

References Cited in the file of this patent UNITED STATES PATENTS Hodges et a1 Feb. 20, 1906 (Original No. 752,554) Moore July 10, 1923 Hahnernann et al. Mar. 3, 1925 Walker June 4, 1929 Rieber Sept. 16, 1930 Brelsford June 23, 1936 Williams Aug. 28, 1945 Morgan May 7, 1946 6 Forbes et al July 1, 1947 McSkirnin Apr. 25, 1950 Howatt May 26, 1953 Uhrig et a1 Sept. 14, 1954 Minnich Apr. 5, 1955 Mendoussc June 28, 1955 Miller Apr. 10, 1956 Green Aug. 28, 1956 Slater Dec. 11, 1956 Davis Apr. 23, 1957 Hollmann Aug. 26, 1958 Camp Dec. 16, 1958 FOREIGN PATENTS Canada May 8, 1956 Great Britain Mar. 16, 1949 OTHER REFERENCES Ultrasonics by Benson Carlin, pub]. by McGraw-Hill, 20 1949, First Ed., pp. 82, 83, 86, 88, 89 relied upon. 

1. A VIBRATILE DISC AND ITS SUPPORT, WHICH COMPRISES A MEMBER HAVING A RECESS OPENING THROUGH A FACE THEREOF, SAID MEMBER HAVING AN ENDLESS RABBET WITH TWO WALLS AT ANGLES TO ONE ANOTHER BORDERING SAID RECESS AND OPENING OUTWARDLY OF THE RECESS AND AT ITS INNER SIDE INTO SAID RECESS, AN ENDLESS ELASTOMERIC ELEMENT DISPOSED IN SAID RABBET AND ABUTTING SAID TWO WALLS OF SAID RABBET, A VIBRATILE DISC HAVING A MARGINAL EDGE FACE SUBSTANTIALLY PERPENDICULAR TO ITS OTHER FACES, DISPOSED ACROSS SAID RECESS WITH ITS SAID MARGINAL EDGE FACE ABUTTING THE INNER PERIPHERY OF SAID ELEMENT, AND MEANS CARRIED BY SAID MEMBER AND ADJUSTABLE THEREON IN A DIRECTION NORMAL TO THE PLANES OF SAID OTHER FACES OF SAID DISC TO CONFINE SAID ELEMENT IN SAID RABBET AND COMPRESS IT AGAINST SAID TWO WALLS AND SAID MARGINAL EDGE FACE UNDER A PRESSURE VARYING WITH THE SAID ADJUSTMENT OF SAID MEANS, THE INNER PERIPHERY OF SAID ELASTOMERIC ELEMENT, IN TRANSVERSE CROSS-SECTION RECEDING OUTWARDLY FROM AND OUT OF CONTACT WITH THE FACES OF SAID DISC, ABUTTING SAID DISC SOLELY ALONG ITS SAID MARGINAL EDGE, AND FORMING THE MAIN SUPPORT FOR SAID DISC. 